The present Invention relates to a damper disc assembly employable in the clutch disc assembly of heavy-duty vehicles.
The torsional damping characteristics (torsional angle versus torque) of damper disc assemblies of this type are such that in effect there is a first, low-rigidity/low torsional hysteretic damping stage and a second, high-rigidity/high torsional hysteretic damping stage. Thus torsional vibration under low loads when the engine is idling is damped through the first response stage; under high loads torsional vibration Is damped through the second response stage of the damper disc assembly.
Under the functional characteristics of the assembly in torsional damping there is a point where the first stage shifts to the second stage, at which the assembly rigidity and the torsional hysteretic damping change rapidly. Under certain vehicle operation conditions in particular, the damper disc assembly may operate in the range including the transition point at which assembly rigidity and torsional hysteretic damping change sharply. Torsional vibration is therein not damped smoothly, giving rise to high-level growling noise due to gearbacklash in the transmission.
A PTO (power takeoff) mechanism equipped with both power take-off as well as drive damper disc assemblies for driving is provided in one type of heavy-duty vehicle. Therein, the power take-off damper disc assembly often is activated in the range of the abrupt stage-shifting point, giving rise to increased noise due to gear backlash and so on.